From 904dd561d0154844e673dd79297c9bc5e4ff4e1e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bence=20Sg=C3=A1netz?= <voidxb@gmail.com>
Date: Wed, 11 Oct 2023 01:05:20 +0200
Subject: [PATCH] FFT1D optimization for low sizes + test

---
 Cavern/Utilities/Measurements.FFT.cs    |  5 ++++-
 Tests/Test.Cavern/Measurements_Tests.cs | 13 +++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/Cavern/Utilities/Measurements.FFT.cs b/Cavern/Utilities/Measurements.FFT.cs
index 8cab362a..b68d4ce8 100644
--- a/Cavern/Utilities/Measurements.FFT.cs
+++ b/Cavern/Utilities/Measurements.FFT.cs
@@ -219,9 +219,12 @@ static void ProcessFFT(float[] samples, FFTCache cache) {
             if (CavernAmp.IsMono()) {
                 ProcessFFT_Mono(even, cache, --depth);
                 ProcessFFT_Mono(odd, cache, depth);
-            } else {
+            } else if (even.Length != 4) {
                 ProcessFFT(even, cache, --depth);
                 ProcessFFT(odd, cache, depth);
+            } else {
+                ProcessFFT4(even);
+                ProcessFFT4(odd);
             }
 
             float[] cosCache = FFTCache.cos[depth + 1],
diff --git a/Tests/Test.Cavern/Measurements_Tests.cs b/Tests/Test.Cavern/Measurements_Tests.cs
index b5f7ebc9..2a6c884f 100644
--- a/Tests/Test.Cavern/Measurements_Tests.cs
+++ b/Tests/Test.Cavern/Measurements_Tests.cs
@@ -54,6 +54,19 @@ public void FFT_IFFT_Sine() {
             }
         }
 
+        /// <summary>
+        /// Tests the FFT variant which optimizes the first step of the FFT to keep an absolute result.
+        /// </summary>
+        [TestMethod, Timeout(1000)]
+        public void FFT1D() {
+            float[] signal = new float[16];
+            signal[0] = 1;
+            float[] fft = signal.FFT1D();
+            for (int i = 0; i < fft.Length; i++) {
+                Assert.IsTrue(fft[i] == 1);
+            }
+        }
+
         /// <summary>
         /// Tests an FFT with a length of 4, which is calling a hardcoded FFT variant.
         /// </summary>